How Linux boots

How Linux boots :

As it turns out, there isn't much to the boot process:

1. A boot loader finds the kernel image on the disk, loads it into memory, and starts it.
2. The kernel initializes the devices and its drivers.
3. The kernel mounts the root filesystem.
4. The kernel starts a program called init.
5. init sets the rest of the processes in motion.
6. The last processes that init starts as part of the boot sequence allow you to log in.

Identifying each stage of the boot process is invaluable in fixing boot problems and understanding the system as a whole. To start, zero in on the boot loader, which is the initial screen or prompt you get after the computer does its power-on self-test, asking which operating system to run. After you make a choice, the boot loader runs the Linux kernel, handing control of the system to the kernel.

There is a detailed discussion of the kernel elsewhere in this book from which this article is excerpted. This article covers the kernel initialization stage, the stage when the kernel prints a bunch of messages about the hardware present on the system. The kernel starts init just after it displays a message proclaiming that the kernel has mounted the root filesystem:

VFS: Mounted root (ext2 filesystem) readonly.

Soon after, you will see a message about init starting, followed by system service startup messages, and finally you get a login prompt of some sort.

NOTE On Red Hat Linux, the init note is especially obvious, because it "welcomes" you to "Red Hat Linux." All messages thereafter show success or failure in brackets at the right-hand side of the screen.

Most of this chapter deals with init, because it is the part of the boot sequence where you have the most control.

init

There is nothing special about init. It is a program just like any other on the Linux system, and you'll find it in /sbin along with other system binaries. The main purpose of init is to start and stop other programs in a particular sequence. All you have to know is how this sequence works.

There are a few different variations, but most Linux distributions use the System V style discussed here. Some distributions use a simpler version that resembles the BSD init, but you are unlikely to encounter this.

Runlevels

At any given time on a Linux system, a certain base set of processes is running. This state of the machine is called its runlevel, and it is denoted with a number from 0 through 6. The system spends most of its time in a single runlevel. However, when you shut the machine down, init switches to a different runlevel in order to terminate the system services in an orderly fashion and to tell the kernel to stop. Yet another runlevel is for single-user mode, discussed later.

The easiest way to get a handle on runlevels is to examine the init configuration file, /etc/inittab. Look for a line like the following:

id:5:initdefault:

 

This line means that the default runlevel on the system is 5. All lines in the inittab file take this form, with four fields separated by colons occurring in the following order:

• # A unique identifier (a short string, such as id in the preceding example)
• The applicable runlevel number(s)
• The action that init should take (in the preceding example, the action is to set the default runlevel to 5)
• A command to execute (optional)

There is no command to execute in the preceding initdefault example because a command doesn't make sense in the context of setting the default runlevel. Look a little further down in inittab, until you see a line like this:

l5:5:wait:/etc/rc.d/rc 5

This line triggers most of the system configuration and services through the rc*.d and init.d directories. You can see that init is set to execute a command called /etc/rc.d/rc 5 when in runlevel 5. The wait action tells when and how init runs the command: run rc 5 once when entering runlevel 5, and then wait for this command to finish before doing anything else.

There are several different actions in addition to initdefault and wait, especially pertaining to power management, and the inittab(5) manual page tells you all about them. The ones that you're most likely to encounter are explained in the following sections.

respawn

The respawn action causes init to run the command that follows, and if the command finishes executing, to run it again. You're likely to see something similar to this line in your inittab file:

1:2345:respawn:/sbin/mingetty tty1

 

The getty programs provide login prompts. The preceding line is for the first virtual console (/dev/tty1), the one you see when you press ALT-F1 or CONTROL-ALT-F1. The respawn action brings the login prompt back after you log out.

ctrlaltdel

The ctrlaltdel action controls what the system does when you press CONTROL-ALT-DELETE on a virtual console. On most systems, this is some sort of reboot command using the shutdown command.

sysinit

The sysinit action is the very first thing that init should run when it starts up, before entering any runlevels.

How processes in runlevels start

You are now ready to learn how init starts the system services, just before it lets you log in. Recall this inittab line from earlier:

l5:5:wait:/etc/rc.d/rc 5

This small line triggers many other programs. rc stands for run commands, and you will hear people refer to the commands as scripts, programs, or services. So, where are these commands, anyway?

For runlevel 5, in this example, the commands are probably either in /etc/rc.d/rc5.d or /etc/rc5.d. Runlevel 1 uses rc1.d, runlevel 2 uses rc2.d, and so on. You might find the following items in the rc5.d directory:

S10sysklogd       S20ppp          S99gpm

S12kerneld        S25netstd_nfs   S99httpd

S15netstd_init    S30netstd_misc  S99rmnologin

S18netbase        S45pcmcia       S99sshd

S20acct           S89atd

S20logoutd        S89cron 

 

The rc 5 command starts programs in this runlevel directory by running the following commands:

S10sysklogd start
S12kerneld start
S15netstd_init start
S18netbase start
...
S99sshd start

 

Notice the start argument in each command. The S in a command name means that the command should run in start mode, and the number (00 through 99) determines where in the sequence rc starts the command.

The rc*.d commands are usually shell scripts that start programs in /sbin or /usr/sbin. Normally, you can figure out what one of the commands actually does by looking at the script with less or another pager program.

You can start one of these services by hand. For example, if you want to start the httpd Web server program manually, run S99httpd start. Similarly, if you ever need to kill one of the services when the machine is on, you can run the command in the rc*.d directory with the stop argument (S99httpd stop, for instance).

Some rc*.d directories contain commands that start with K (for "kill," or stop mode). In this case, rc runs the command with the stop argument instead of start. You are most likely to encounter K commands in runlevels that shut the system down.

Adding and removing services

If you want to add, delete, or modify services in the rc*.d directories, you need to take a closer look at the files inside. A long listing reveals a structure like this:

lrwxrwxrwx . . . S10sysklogd -> ../init.d/sysklogd
lrwxrwxrwx . . . S12kerneld -> ../init.d/kerneld
lrwxrwxrwx . . . S15netstd_init -> ../init.d/netstd_init
lrwxrwxrwx . . . S18netbase -> ../init.d/netbase
...

 

The commands in an rc*.d directory are actually symbolic links to files in an init.d directory, usually in /etc or /etc/rc.d. Linux distributions contain these links so that they can use the same startup scripts for all runlevels. This convention is by no means a requirement, but it often makes organization a little easier.

To prevent one of the commands in the init.d directory from running in a particular runlevel, you might think of removing the symbolic link in the appropriate rc*.d directory. This does work, but if you make a mistake and ever need to put the link back in place, you might have trouble remembering the exact name of the link. Therefore, you shouldn't remove links in the rc*.d directories, but rather, add an underscore (_) to the beginning of the link name like this:

mv S99httpd _S99httpd

 

At boot time, rc ignores _S99httpd because it doesn't start with S or K. Furthermore, the original name is still obvious, and you have quick access to the command if you're in a pinch and need to start it by hand.

To add a service, you must create a script like the others in the init.d directory and then make a symbolic link in the correct rc*.d directory. The easiest way to write a script is to examine the scripts already in init.d, make a copy of one that you understand, and modify the copy.

When adding a service, make sure that you choose an appropriate place in the boot sequence to start the service. If the service starts too soon, it may not work, due to a dependency on some other service. For non-essential services, most systems administrators prefer numbers in the 90s, after most of the services that came with the system.

Linux distributions usually come with a command to enable and disable services in the rc*.d directories. For example, in Debian, the command is update-rc.d, and in Red Hat Linux, the command is chkconfig. Graphical user interfaces are also available. Using these programs helps keep the startup directories consistent and helps with upgrades.

HINT: One of the most common Linux installation problems is an improperly configured XFree86 server that flicks on and off, making the system unusable on console. To stop this behavior, boot into single-user mode and alter your runlevel or runlevel services. Look for something containing xdm, gdm, or kdm in your rc*.d directories, or your /etc/inittab.

Controlling init

Occasionally, you need to give init a little kick to tell it to switch runlevels, to re-read the inittab file, or just to shut down the system. Because init is always the first process on a system, its process ID is always 1.

You can control init with telinit. For example, if you want to switch to runlevel 3, use this command:

telinit 3

When switching runlevels, init tries to kill off any processes that aren't in the inittab file for the new runlevel. Therefore, you should be careful about changing runlevels.

When you need to add or remove respawning jobs or make any other change to the inittab file, you must tell init about the change and cause it to re-read the file. Some people use kill -HUP 1 to tell init to do this. This traditional method works on most versions of Unix, as long as you type it correctly. However, you can also run this telinit command:

telinit q

You can also use telinit s to switch to single-user mode.

Shutting down

init also controls how the system shuts down and reboots. The proper way to shut down a Linux machine is to use the shutdown command.

There are two basic ways to use shutdown. If you halt the system, it shuts the machine down and keeps it down. To make the machine halt immediately, use this command:

shutdown -h now

On most modern machines with reasonably recent versions of Linux, a halt cuts the power to the machine. You can also reboot the machine. For a reboot, use -r instead of -h.

The shutdown process takes several seconds. You should never reset or power off a machine during this stage.

In the preceding example, now is the time to shut down. This argument is mandatory, but there are many ways of specifying it. If you want the machine to go down sometime in the future, one way is to use +n, where n is the number of minutes shutdown should wait before doing its work. For other options, look at the shutdown(8) manual page.

To make the system reboot in 10 minutes, run this command:

shutdown -r +10

On Linux, shutdown notifies anyone logged on that the machine is going down, but it does little real work. If you specify a time other than now, shutdown creates a file called /etc/nologin. When this file is present, the system prohibits logins by anyone except the superuser.

When system shutdown time finally arrives, shutdown tells init to switch to runlevel 0 for a halt and runlevel 6 for a reboot. When init enters runlevel 0 or 6, all of the following takes place, which you can verify by looking at the scripts inside rc0.d and rc6.d:

1. init kills every process that it can (as it would when switching to any other runlevel).

• The initial rc0.d/rc6.d commands run, locking system files into place and making other preparations for shutdown.
• The next rc0.d/rc6.d commands unmount all filesystems other than the root.
• Further rc0.d/rc6.d commands remount the root filesystem read-only.
• Still more rc0.d/rc6.d commands write all buffered data out to the filesystem with the sync program.
• The final rc0.d/rc6.d commands tell the kernel to reboot or stop with the reboot, halt, or poweroff program.

The reboot and halt programs behave differently for each runlevel, potentially causing confusion. By default, these programs call shutdown with the -r or -h options, but if the system is already at the halt or reboot runlevel, the programs tell the kernel to shut itself off immediately. If you really want to shut your machine down in a hurry (disregarding any possible damage from a disorderly shutdown), use the -f option.

 

BandWidth Explained

BandWidth Explained

Most hosting companies offer a variety of bandwidth options in their plans. So exactly what is bandwidth as it relates to web hosting? Put simply, bandwidth is the amount of traffic that is allowed to occur between your web site and the rest of the internet. The amount of bandwidth a hosting company can provide is determined by their network connections, both internal to their data center and external to the public internet.

Network Connectivity :

The internet, in the most simplest of terms, is a group of millions of computers connected by networks. These connections within the internet can be large or small depending upon the cabling and equipment that is used at a particular internet location. It is the size of each network connection that determines how much bandwidth is available. For example, if you use a DSL connection to connect to the internet, you have 1.54 Mega bits (Mb) of bandwidth. Bandwidth therefore is measured in bits (a single 0 or 1). Bits are grouped in bytes which form words, text, and other information that is transferred between your computer and the internet.

If you have a DSL connection to the internet, you have dedicated bandwidth between your computer and your internet provider. But your internet provider may have thousands of DSL connections to their location. All of these connection aggregate at your internet provider who then has their own dedicated connection to the internet (or multiple connections) which is much larger than your single connection. They must have enough bandwidth to serve your computing needs as well as all of their other customers. So while you have a 1.54Mb connection to your internet provider, your internet provider may have a 255Mb connection to the internet so it can accommodate your needs and up to 166 other users (255/1.54).

Traffic :

A very simple analogy to use to understand bandwidth and traffic is to think of highways and cars. Bandwidth is the number of lanes on the highway and traffic is the number of cars on the highway. If you are the only car on a highway, you can travel very quickly. If you are stuck in the middle of rush hour, you may travel very slowly since all of the lanes are being used up.

Traffic is simply the number of bits that are transferred on network connections. It is easiest to understand traffic using examples. One Gigabyte is 2 to the 30th power (1,073,741,824) bytes. One gigabyte is equal to 1,024 megabytes. To put this in perspective, it takes one byte to store one character. Imagine 100 file cabinets in a building, each of these cabinets holds 1000 folders. Each folder has 100 papers. Each paper contains 100 characters - A GB is all the characters in the building. An MP3 song is about 4MB, the same song in wav format is about 40MB, a full length movie can be 800MB to 1000MB (1000MB = 1GB).

If you were to transfer this MP3 song from a web site to your computer, you would create 4MB of traffic between the web site you are downloading from and your computer. Depending upon the network connection between the web site and the internet, the transfer may occur very quickly, or it could take time if other people are also downloading files at the same time. If, for example, the web site you download from has a 10MB connection to the internet, and you are the only person accessing that web site to download your MP3, your 4MB file will be the only traffic on that web site. However, if three people are all downloading that same MP at the same time, 12MB (3 x 4MB) of traffic has been created. Because in this example, the host only has 10MB of bandwidth, someone will have to wait. The network equipment at the hosting company will cycle through each person downloading the file and transfer a small portion at a time so each person's file transfer can take place, but the transfer for everyone downloading the file will be slower. If 100 people all came to the site and downloaded the MP3 at the same time, the transfers would be extremely slow. If the host wanted to decrease the time it took to download files simultaneously, it could increase the bandwidth of their internet connection (at a cost due to upgrading equipment).

Hosting Bandwidth :

In the example above, we discussed traffic in terms of downloading an MP3 file. However, each time you visit a web site, you are creating traffic, because in order to view that web page on your computer, the web page is first downloaded to your computer (between the web site and you) which is then displayed using your browser software (Internet Explorer, Netscape, etc.) . The page itself is simply a file that creates traffic just like the MP3 file in the example above (however, a web page is usually much smaller than a music file).

A web page may be very small or large depending upon the amount of text and the number and quality of images integrated within the web page. For example, the home page for CNN.com is about 200KB (200 Kilobytes = 200,000 bytes = 1,600,000 bits). This is typically large for a web page. In comparison, Yahoo's home page is about 70KB.

How Much Bandwidth Is Enough?

It depends (don't you hate that answer). But in truth, it does. Since bandwidth is a significant determinant of hosting plan prices, you should take time to determine just how much is right for you. Almost all hosting plans have bandwidth requirements measured in months, so you need to estimate the amount of bandwidth that will be required by your site on a monthly basis

If you do not intend to provide file download capability from your site, the formula for calculating bandwidth is fairly straightforward:

Average Daily Visitors x Average Page Views x Average Page Size x 31 x Fudge Factor

If you intend to allow people to download files from your site, your bandwidth calculation should be:

[(Average Daily Visitors x Average Page Views x Average Page Size) + (Average Daily File Downloads x Average File Size)] x 31 x Fudge Factor

Let us examine each item in the formula:
Average Daily Visitors - The number of people you expect to visit your site, on average, each day. Depending upon how you market your site, this number could be from 1 to 1,000,000.

Average Page Views - On average, the number of web pages you expect a person to view. If you have 50 web pages in your web site, an average person may only view 5 of those pages each time they visit.

Average Page Size - The average size of your web pages, in Kilobytes (KB). If you have already designed your site, you can calculate this directly.

Average Daily File Downloads - The number of downloads you expect to occur on your site. This is a function of the numbers of visitors and how many times a visitor downloads a file, on average, each day.

Average File Size - Average file size of files that are downloadable from your site. Similar to your web pages, if you already know which files can be downloaded, you can calculate this directly.

Fudge Factor - A number greater than 1. Using 1.5 would be safe, which assumes that your estimate is off by 50%. However, if you were very unsure, you could use 2 or 3 to ensure that your bandwidth requirements are more than met.

Usually, hosting plans offer bandwidth in terms of Gigabytes (GB) per month. This is why our formula takes daily averages and multiplies them by 31.

Summary :

Most personal or small business sites will not need more than 1GB of bandwidth per month. If you have a web site that is composed of static web pages and you expect little traffic to your site on a daily basis, go with a low bandwidth plan. If you go over the amount of bandwidth allocated in your plan, your hosting company could charge you over usage fees, so if you think the traffic to your site will be significant, you may want to go through the calculations above to estimate the amount of bandwidth required in a hosting plan.

 

UNIX - LINUX Interview Questions and Answers :

1. How are devices represented in UNIX?

All devices are represented by files called special files that are located in/dev directory. Thus, device files and other files are named and accessed in the same way. A 'regular file' is just an ordinary data file in the disk. A 'block special file' represents a device with characteristics similar to a disk (data transfer in terms of blocks). A 'character special file' represents a device with characteristics similar to a keyboard (data transfer is by stream of bits in sequential order).

2. What is 'inode'?

All UNIX files have its description stored in a structure called 'inode'. The inode contains info about the file-size, its location, time of last access, time of last modification, permission and so on. Directories are also represented as files and have an associated inode. In addition to descriptions about the file, the inode contains pointers to the data blocks of the file. If the file is large, inode has indirect pointer to a block of pointers to additional data blocks (this further aggregates for larger files). A block is typically 8k.
Inode consists of the following fields:

• File owner identifier
• File type
• File access permissions
• File access times
• Number of links
• File size
• Location of the file data

3. Brief about the directory representation in UNIX

A Unix directory is a file containing a correspondence between filenames and inodes. A directory is a special file that the kernel maintains. Only kernel modifies directories, but processes can read directories. The contents of a directory are a list of filename and inode number pairs. When new directories are created, kernel makes two entries named '.' (refers to the directory itself) and '..' (refers to parent directory).
System call for creating directory is mkdir (pathname, mode).

4. What are the Unix system calls for I/O?

• open(pathname,flag,mode) - open file
• creat(pathname,mode) - create file
• close(filedes) - close an open file
• read(filedes,buffer,bytes) - read data from an open file
• write(filedes,buffer,bytes) - write data to an open file
• lseek(filedes,offset,from) - position an open file
• dup(filedes) - duplicate an existing file descriptor
• dup2(oldfd,newfd) - duplicate to a desired file descriptor
• fcntl(filedes,cmd,arg) - change properties of an open file
• ioctl(filedes,request,arg) - change the behaviour of an open file

The difference between fcntl anf ioctl is that the former is intended for any open file, while the latter is for device-specific operations.

5. How do you change File Access Permissions?

Every file has following attributes:
owner's user ID ( 16 bit integer )
owner's group ID ( 16 bit integer )
File access mode word

'r w x -r w x- r w x'

(user permission-group permission-others permission)
r-read, w-write, x-execute
To change the access mode, we use chmod(filename,mode).
Example 1:
To change mode of myfile to 'rw-rw-r–' (ie. read, write permission for user - read,write permission for group - only read permission for others) we give the args as:
chmod(myfile,0664) .
Each operation is represented by discrete values

'r' is 4
'w' is 2
'x' is 1

Therefore, for 'rw' the value is 6(4+2).
Example 2:
To change mode of myfile to 'rwxr–r–' we give the args as:

chmod(myfile,0744).

 

6. What are links and symbolic links in UNIX file system?

A link is a second name (not a file) for a file. Links can be used to assign more than one name to a file, but cannot be used to assign a directory more than one name or link filenames on different computers.
Symbolic link 'is' a file that only contains the name of another file.Operation on the symbolic link is directed to the file pointed by the it.Both the limitations of links are eliminated in symbolic links.
Commands for linking files are:

Link ln filename1 filename2
Symbolic link ln -s filename1 filename2

7. What is a FIFO?

FIFO are otherwise called as 'named pipes'. FIFO (first-in-first-out) is a special file which is said to be data transient. Once data is read from named pipe, it cannot be read again. Also, data can be read only in the order written. It is used in interprocess communication where a process writes to one end of the pipe (producer) and the other reads from the other end (consumer).

8. How do you create special files like named pipes and device files?

The system call mknod creates special files in the following sequence.
1. kernel assigns new inode,
2. sets the file type to indicate that the file is a pipe, directory or special file,
3. If it is a device file, it makes the other entries like major, minor device numbers.
For example:
If the device is a disk, major device number refers to the disk controller and minor device number is the disk.

9. Discuss the mount and unmount system calls

The privileged mount system call is used to attach a file system to a directory of another file system; the unmount system call detaches a file system. When you mount another file system on to your directory, you are essentially splicing one directory tree onto a branch in another directory tree. The first argument to mount call is the mount point, that is , a directory in the current file naming system. The second argument is the file system to mount to that point. When you insert a cdrom to your unix system's drive, the file system in the cdrom automatically mounts to /dev/cdrom in your system.

10. How does the inode map to data block of a file?

Inode has 13 block addresses. The first 10 are direct block addresses of the first 10 data blocks in the file. The 11th address points to a one-level index block. The 12th address points to a two-level (double in-direction) index block. The 13th address points to a three-level(triple in-direction)index block. This provides a very large maximum file size with efficient access to large files, but also small files are accessed directly in one disk read.

11. What is a shell?

A shell is an interactive user interface to an operating system services that allows an user to enter commands as character strings or through a graphical user interface. The shell converts them to system calls to the OS or forks off a process to execute the command. System call results and other information from the OS are presented to the user through an interactive interface. Commonly used shells are sh,csh,ks etc.

12. Brief about the initial process sequence while the system boots up.

While booting, special process called the 'swapper' or 'scheduler' is created with Process-ID 0. The swapper manages memory allocation for processes and influences CPU allocation. The swapper inturn creates 3 children:

• the process dispatcher,
• vhand and
• dbflush

with IDs 1,2 and 3 respectively.
This is done by executing the file /etc/init. Process dispatcher gives birth to the shell. Unix keeps track of all the processes in an internal data structure called the Process Table (listing command is ps -el).

13. What are various IDs associated with a process?

Unix identifies each process with a unique integer called ProcessID. The process that executes the request for creation of a process is called the 'parent process' whose PID is 'Parent Process ID'. Every process is associated with a particular user called the 'owner' who has privileges over the process. The identification for the user is 'UserID'. Owner is the user who executes the process. Process also has 'Effective User ID' which determines the access privileges for accessing resources like files.

• getpid() -process id
• getppid() -parent process id
• getuid() -user id
• geteuid() -effective user id

14. Explain fork() system call.

The `fork()' used to create a new process from an existing process. The new process is called the child process, and the existing process is called the parent. We can tell which is which by checking the return value from `fork()'. The parent gets the child's pid returned to him, but the child gets 0 returned to him.

15. Predict the output of the following program code

main()
{
  fork();
  printf("Hello World!");
}

Answer:

Hello World!Hello World!

Explanation:
The fork creates a child that is a duplicate of the parent process. The child begins from the fork().All the statements after the call to fork() will be executed twice.(once by the parent process and other by child). The statement before fork() is executed only by the parent process.

16. Predict the output of the following program code

main()
{
fork(); fork(); fork();
printf("Hello World!");
}

Answer:
"Hello World" will be printed 8 times.
Explanation:
2^n times where n is the number of calls to fork()

17. List the system calls used for process management:

System calls Description

• fork() To create a new process
• exec() To execute a new program in a process
• wait() To wait until a created process completes its execution
• exit() To exit from a process execution
• getpid() To get a process identifier of the current process
• getppid() To get parent process identifier
• nice() To bias the existing priority of a process
• brk() To increase/decrease the data segment size of a process.

18. How can you get/set an environment variable from a program?

Getting the value of an environment variable is done by using `getenv()'. Setting the value of an environment variable is done by using `putenv()'.

19. How can a parent and child process communicate?

A parent and child can communicate through any of the normal inter-process communication schemes (pipes, sockets, message queues, shared memory), but also have some special ways to communicate that take advantage of their relationship as a parent and child. One of the most obvious is that the parent can get the exit status of the child.

20. What is a zombie?

When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might need it - for example, the parent may need to check the child's exit status. To be able to get this information, the parent calls `wait()'; In the interval between the child terminating and the parent calling `wait()', the child is said to be a `zombie' (If you do `ps', the child will have a `Z' in its status field to indicate this.)

21. What are the process states in Unix?

As a process executes it changes state according to its circumstances. Unix processes have the following states:
Running : The process is either running or it is ready to run .
Waiting : The process is waiting for an event or for a resource.
Stopped : The process has been stopped, usually by receiving a signal.
Zombie : The process is dead but have not been removed from the process table.

 

Networking Interview Questions and Answers :

1. What is an Object server?

With an object server, the Client/Server application is written as a set of communicating objects. Client object communicate with server objects using an Object Request Broker (ORB). The client invokes a method on a remote object. The ORB locates an instance of that object server class, invokes the requested method and returns the results to the client object. Server objects must provide support for concurrency and sharing. The ORB brings it all together.

2. What is a Transaction server?

With a transaction server, the client invokes remote procedures that reside on the server with an SQL database engine. These remote procedures on the server execute a group of SQL statements. The network exchange consists of a single request/reply message. The SQL statements either all succeed or fail as a unit.

3. What is a Database Server?

With a database server, the client passes SQL requests as messages to the database server. The results of each SQL command are returned over the network. The server uses its own processing power to find the request data instead of passing all the records back to the client and then getting it find its own data. The result is a much more efficient use of distributed processing power. It is also known as SQL engine.

4. What are the most typical functional units of the Client/Server applications?

• User interface
• Business Logic and
• Shared data.

5. What are all the Extended services provided by the OS?

• Ubiquitous communications
• Network OS extension
• Binary large objects (BLOBs)
• Global directories and Network yellow pages
• Authentication and Authorization services
• System management
• Network time
• Database and transaction services
• Internet services
• Object- oriented services

6. What are Triggers and Rules?

Triggers are special user defined actions usually in the form of stored procedures, that are automatically invoked by the server based on data related events. It can perform complex actions and can use the full power of procedural languages.
A rule is a special type of trigger that is used to perform simple checks on data.

7. What is meant by Transparency?

Transparency really means hiding the network and its servers from the users and even the application programmers.

8. What are TP-Lite and TP-Heavy Monitors?

TP-Lite is simply the integration of TP Monitor functions in the database engines. TP-Heavy are TP Monitors which supports the Client/Server architecture and allow PC to initiate some very complex multiserver transaction from the desktop.

9. What are the two types of OLTP?

TP lite, based on stored procedures. TP heavy, based on the TP monitors.

10. What is a Web server?

This new model of Client/Server consists of thin, protable, "universal" clients that talk to superfat servers. In the simplet form, a web server returns documents when clients ask for them by name. The clients and server communicate using an RPC-like protocol called HTTP.
11. What are Super servers?

These are fully-loaded machines which includes multiprocessors, high-speed disk arrays for intervive I/O and fault tolerant features.

12. What is a TP Monitor?

There is no commonly accepted definition for a TP monitor. According to Jeri Edwards' a TP Monitor is "an OS for transaction processing".

13. TP Monitor does mainly two things extremely well. They are Process management and Transaction management.?

They were originally introduced to run classes of applications that could service hundreds and sometimes thousands of clients. TP Monitors provide an OS - on top of existing OS - that connects in real time these thousands of humans with a pool of shared server processes.

14. What is meant by Asymmetrical protocols?

There is a many-to-one relationship between clients and server. Clients always initiate the dialog by requesting a service. Servers are passively awaiting for requests from clients.

15. What are the types of Transparencies?

The types of transparencies the NOS middleware is expected to provide are:-

• Location transparency
• Namespace transparency
• Logon transparency
• Replication transparency
• Local/Remote access transparency
• Distributed time transparency
• Failure transparency and
• Administration transparency.

16. What is the difference between trigger and rule?

The triggers are called implicitly by database generated events, while stored procedures are called explicitly by client applications.

17. What are called Transactions?

The grouped SQL statements are called Transactions (or) A transaction is a collection of actions embused with ACID properties.

18. What are the building blocks of Client/Server?

• The client
• The server and
• Middleware.

19. Explain the building blocks of Client/Server?

The client side building block runs the client side of the application.
The server side building block runs the server side of the application.

20. The middleware buliding block runs on both the client and server sides of an application. It is broken into three categories:-

• Transport stack
• Network OS
• Service-specific middleware.

21. What are all the Base services provided by the OS?

• Task preemption
• Task priority
• Semaphores
• Interprocess communications (IPC)
• Local/Remote Interprocess communication
• Threads
• Intertask protection
• Multiuser
• High performance file system
• Efficient memory management and
• Dynamically linked Run-time extensions.

22. What are the roles of SQL?

• SQL is an interactive query language for ad hoc database queries.
• SQL is a database programming language.
• SQL is a data definition and data administration language.
• SQL is the language of networked database servers
• SQL helps protect the data in a multi-user networked environment.
• Because of these multifacted roles it plays, physicists might call SQL as "The grand unified theory of database".

23. What is Structured Query Langauge (SQL)?

SQL is a powerful set-oriented language which was developed by IBM research for the databases that adhere to the relational model. It consists of a short list of powerful, yet highly flexible, commands that can be used to manipulate information collected in tables. Through SQL, we can manipulate and control sets of records at a time.

24. What are the characteristics of Client/Server?

• Service
• Shared resources
• Asymmentrical protocols
• Transparency of location
• Mix-and-match
• Message based exchanges
• Encapsulation of services
• Scalability
• Integrity

Client/Server computing is the ultimate "Open platform". It gives the freedom to mix-and-match components of almost any level. Clients and servers are loosely coupled systems that interact through a message-passing mechanism.

25. What is Remote Procedure Call (RPC)?

RPC hides the intricacies of the network by using the ordinary procedure call mechanism familiar to every programmer. A client process calls a function on a remote server and suspends itself until it gets back the results. Parameters are passed like in any ordinary procedure. The RPC, like an ordinary procedure, is synchoronous. The process that issues the call waits until it gets the results.

Under the covers, the RPC run-time software collects values for the parameters, forms a message, and sends it to the remote server. The server receives the request, unpack the parameters, calls the procedures, and sends the reply back to the client. It is a telephone-like metaphor.

26. What are the main components of Transaction-based Systems?

• Resource Manager
• Transaction Manager and
• Application Program.

27. What are the three types of SQL database server architecture?

• Process-per-client Architecture. (Example: Oracle 6, Informix )
• Multithreaded Architecture. (Example: Sybase, SQL server)
• Hybrid Architecture (Example: Oracle 7)

28. What are the Classification of clients?

Non-GUI clients - Two types are:-

1. Non-GUI clients that do not need multi-tasking
   (Example: Automatic Teller Machines (ATM), Cell phone)
2. Non-GUI clients that need multi-tasking
   (Example: ROBOTs)
   GUI clients
   OOUI clients

29. What are called Non-GUI clients, GUI Clients and OOUI Clients?

Non-GUI Client: These are applications, generate server requests with a minimal amount of human interaction.
GUI Clients: These are applicatoins, where occassional requests to the server result from a human interacting with a GUI
(Example: Windows 3.x, NT 3.5)
OOUI clients : These are applications, which are highly-iconic, object-oriented user interface that provides seamless access to information in very visual formats.
(Example: MAC OS, Windows 95, NT 4.0)

30. What is Message Oriented Middleware (MOM)?

MOM allows general purpose messages to be exchanged in a Client/Server system using message queues. Applications communicate over networks by simply putting messages in the queues and getting messages from queues. It typically provides a very simple high level APIs to its services.
MOM's messaging and queuing allow clients and servers to communicate across a network without being linked by a private, dedicated, logical connection. The clients and server can run at different times. It is a post-office like metaphor.

31. What is meant by Middleware?

Middleware is a distributed software needed to support interaction between clients and servers. In short, it is the software that is in the middle of the Client/Server systems and it acts as a bridge between the clients and servers. It starts with the API set on the client side that is used to invoke a service and it covers the transmission of the request over the network and the resulting response.
It neither includes the software that provides the actual service - that is in the servers domain nor the user interface or the application login - that's in clients domain.

32. What are the functions of the typical server program?

It waits for client-initiated requests. Executes many requests at the same time. Takes care of VIP clients first. Initiates and runs background task activity. Keeps running. Grown bigger and faster.

33. What is meant by Symmentric Multiprocessing (SMP)?

It treats all processors as equal. Any processor can do the work of any other processor. Applications are divided into threads that can run concurrently on any available processor. Any processor in the pool can run the OS kernel and execute user-written threads.

34. What are Service-specific middleware?

It is needed to accomplish a particular Client/Server type of services which includes:-

• Database specific middleware
• OLTP specific middleware
• Groupware specific middleware
• Object specific middleware
• Internet specific middleware and
• System management specific middleware.

35. What are General Middleware?

It includes the communication stacks, distributed directories, authentication services, network time, RPC, Queuing services along with the network OS extensions such as the distributed file and print services.

36. What is meant by Asymmetric Multiprocessing (AMP)?

It imposses hierarchy and a division of labour among processors. Only one designated processor, the master, controls (in a tightly coupled arrangement) slave processors dedicated to specific functions.

37. What is OLTP?

In the transaction server, the client component usually includes GUI and the server components usually consists of SQL transactions against a database. These applications are called OLTP (Online Transaction Processing) OLTP Applications typically,
Receive a fixed set of inputs from remote clients. Perform multiple pre-compiled SQL comments against a local database. Commit the work and Return a fixed set of results.

38. What is meant by 3-Tier architecture?

In 3-tier Client/Server systems, the application logic (or process) lives in the middle tier and it is separated from the data and the user interface. In theory, the 3-tier Client/Server systems are more scalable, robust and flexible.
Example: TP monitor, Web.

39. What is meant by 2-Tier architecture?

In 2-tier Client/Server systems, the application logic is either burried inside the user interface on the client or within the database on the server.
Example: File servers and Database servers with stored procedures.

40. What is Load balancing?

If the number of incoming clients requests exceeds the number of processes in a server class, the TP Monitor may dynamically start new ones and this is called Load balancing.

41. What are called Fat clients and Fat servers?

If the bulk of the application runs on the Client side, then it is Fat clients. It is used for decision support and personal software.
If the bulk of the application runs on the Server side, then it is Fat servers. It tries to minimize network interchanges by creating more abstract levels of services.

42. What is meant by Horizontal scaling and Vertical scaling?

Horizontal scaling means adding or removing client workstations with only a slight performance impact. Vertical scaling means migrating to a larger and faster server machine or multiservers.

43. What is Groupware server?

Groupware addresses the management of semi-structured information such as text, image, mail, bulletin boards and the flow of work. These Client/Server systems have people in direct contact with other people.

44. What are the two broad classes of middleware?

• General middleware
• Service-specific middleware.

45. What are the types of Servers?

• File servers
• Database servers Transaction servers Groupware servers
• Object servers Web servers.

46. What is a File server?

File servers are useful for sharing files across a network. With a file server, the client passes requests for file records over nerwork to file server.

47. What are the five major technologies that can be used to create Client/Server applications?

• Database Servers
• TP Monitors
• Groupware
• Distributed Objects
• Intranets.

48. What is Client/Server?

Clients and Servers are separate logical entities that work together over a network to accomplish a task. Many systems with very different architectures that are connected together are also called Client/Server.

49. List out the benefits obtained by using the Client/Server oriented TP Monitors?

• Client/Server applications development framework.
• Firewalls of protection.
• High availability.
• Load balancing.
• MOM integration.
• Scalability of functions.
• Reduced system cost.

50. What are the services provided by the Operating System?

Extended services - These are add-on modular software components that are layered on top of base service.

 

How to Configure DHCP in your PC..

How to Configure DHCP in your PC..

Dynamic Host Configuration Protocol (DHCP) is the configuration of your Internet Protocol (IP) address, subnet mask, DNS servers, domain name suffix and about 200 other possible options to let your computer communicate with a network automatically via a server or router. It sounds complicated, but once set up, it can make connecting to a network much easier.

Steps :

1. Log into Windows XP with administrator rights. This makes setting up the network for you, and other users, easier as you can make all the necessary changes to settings.
2. Look for the Network Neighborhood or My Network Places icon in your desktop. If it is not there, try your Start Menu.
   Right-click the Network Neighborhood/ My Network Places icon. A drop-down menu will appear.
3. Choose the "Properties" option, generally found at the bottom of the menu.
4. Look for an icon named "Local Area Connection". The icon looks like a pair of computer connected by a link. Double-click this icon.
5. Click the "General" tab, if it is not already selected. You will see a list of protocols to choose form.
6. Scroll down and choose Internet Protocol (TCP/IP), and then click the button that is labeled "Properties" .
7. Again, click the "General" tab, it it is not alreay selected. You will see two choices:
• "Obtain an IP address Automatically"
• "Use the following IP address..."
8. Choose option 1

You have effectively configured DHCP for your PC. When your computer obtains the IP address, it will also obtain DNS server information automatically. This is provided by your dhcp server.

Tips :

1. Make sure your NIC (Network Card)is working properly.
2. Make sure you are connected directly to a router, switch or hub.
3. Make sure the Link light is on. (small green light where the cable plugs into the computer)
4. If you are connected to a LAN, make sure that you have a router that will give addresses away, since the address will be obtained by the PC from the router.
5. If you have a Server on the LAN such as Windows 2000 or 2003, make sure the server is configured DHCP enabled as well.

 

Setting up a VPN in Windows is a two step process.

Setting up a VPN in Windows is a two step process:

• Set up one computer to share files (server).
• Set up another computer to access them (client).

Begin by setting up the server:
Open Internet Explorer and go to www.whatismyip.com. Write down the IP address. You will need it to configure the client.

1. Click the Start button and click Run.
2. Type control and hit Enter.
3. Click Network and Internet Connections.
4. Click Network Connections .
5. Click Create a New Connection, which is the first option on the left toolbar.
6. The New Connection Wizard will open. Click Next.
7. Choose Set up an advanced connection, the last element on the list. Click Next .
8. Choose Accept incoming connections. Click Next.
9. You will see the Devices for Incoming Connections screen.
10. Do not select anything on this screen. Click Next.
11. Select Allow virtual private connections. Click Next.
12. Select to whom you want to give access. Click Next. If a user is not listed, you will have to add an account. See "Related Wikihows" for more information.
13. Do not change anything on the Networking Software screen. Click Next.

That's it! Your computer is now set up to allow for VPNs. Click Finish to complete the wizard.

Now proceed to connect the client:

• Click the Start button and click Run.
• Type control and hit Enter.
• Click Network and Internet Connections.
• Click Network Connections.
• Click Create a New Connection, which is the first option on the left toolbar.
• The New Connection Wizard will open. Click Next.
• Select Connect to the network at my workplace and click Next.
• Select Virtual Private Network connection and click Next.
• Type the name of your network in the blank box. Click Next.
• Enter the IP address you wrote down earlier and click Next.
• Select Add a shortcut to this connection to my desktop and click Finish.

Tips :

14. Both computers must be connected to the internet.
15. The user name and password must be entered exactly as you saved them.
16. The IP address must be written exactly as listed on the screen.
17. If the VPN doesn't work, turn off your firewall.

Warnings :

Do not give access to the "guest" account. It does not require a password, allowing anyone to access the VPN.

 

Some GK Questions

1.What is the expansion of YAHOO?

Yet Another Hierarchy of Officious Oracle

2.What is the expansion of ADIDAS?

ADIDAS- All Day I Dream About Sports

3 .Expansion of Star as in Star TV Network?

Satellite Television Asian Region

4.What is expansion of "ICICI ?"

Industrial credit and Investments Corporation of India

5.What does "baker's dozen" signify?

A baker's dozen consists of 13 items - 1 more than the items
in a normal dozen

6. The 1984-85 season. 2nd ODI between India and Pakistan at Sialkot- India 210/3 with Vengsarkar 94*. Match abandoned. Why?

That match was abandoned after ppl heard the news of indira
gandhi being killed.

7. Who is the only man to have written the National Anthems for two different countries?

Rabindranath Tagore who wrote national anthem for two different countries one is our 's National anthem and another one is for Bangladesh- (Amar Sonar Bangla)

8.From what four word ex-pression does the word 'goodbye' derive?

Goodbye comes from the ex-pression: 'god be with you'.

9.How was Agnes Gonxha Bojaxhiu better known?

Agnes Gonxha Bojaxhiu is none other Mother Teresa.

10.Name the only other country to have got independence on Aug 15th?

South Korea .

11.Why was James Bond Associated with the Number 007?

Because 007 is the ISD code for Russia (or the USSR , as it was known during the cold war)

12.Who faced the first ball in the first ever One day match?

Geoffrey Boycott

13. Which cricketer played for South Africa before it was banned from international cricket and later represented Zimbabwe ?

John Traicos

14. The faces of which four Presidents are carved at Mt.Rushmore?

George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln

15. Which is the only country that is surrounded from all sides by only one country(other than Vatican ) ?

Lesotho surrounded from all sides by South Africa .

 

What is High-Definition TV

What is High-Definition TV :

There are a lot of misconceptions, a lot of products, and some scams out there when looking to purchase an HDTV. Being that it is still relatively new to most people, it can be a confusing time, especially when the next gen consoles are going to make you want to purchase an HDTV.

First, an overview of what "HDTV" is:

Traditionally, TV has been broadcast at 480i. This means 480 interlaced. The frame of the picture is scanned every other line down, and then once again every other line up, which then creates the frame for that specific sequence.

There is also "EDTV", which stands for "enhanced definition television". More or less this is 480p, or 480 progressive, which means the entire frame for that particular shot is scanned in one pass, which creates a clearer picture with virtually no flicker. More or less if you see a set advertised as an EDTV, about the most performance you will get out of it is a set that will be able to support an incoming signal from a progressive scan DVD player, or a game console which is able to send a 480p signal.

 

Enter HDTV, which has a couple different formats. 720p, and 1080i respectively. Right now these are the two formats battling for supremacy in HDTV land. 1080i is the standard used for most stations now, with ABC and ESPN (possibly a couple others) still hanging on to 720p.

When dealing with HDTV sets, they each have their own native display format. This means the signal which it can support as displaying without alteration of that signal via downconverting or upconverting (which I will touch on in a minute) This native display will either be 1080i or 720p. Most, if not all, LCD fixed displays will support 720p natively. Most RPTV's, CRT's - will support 1080i natively.

Here comes the tricky part. A lot of the less expensive sets out there, and even some of the others, will only accept either a 720p signal, or 1080i signal. If it sees a signal come in that it doesn't natively support, the set will downconvert the signal to 480p automatically so it can display the image. For example, you have a 51" Model WS500/510 that displays 1080i as it's native resolution. The program you are trying to view, or the game you are trying to play, is transmitting at 720p. This particular set will see the 720p signal, and downconvert this to 480p. Making this particular set, when receiving anything but 1080i native signals, essentially nothing more than a glorified EDTV.

There are now more and more sets coming out that will finally upconvert. For instance, the 34" Sony CRT tube based HDTV set. If this set sees a 720p signal coming, it will automatically upconvert the signal to 1080i so as to still receive the signal in high-definition. The basis for all this is to make sure that you are purchasing a set which will upconvert 720p to 1080i if you are going with a set that natively supports 1080i, and not downconvert to 480p. This is very important, and should be reflected in your purchase. Especially when games on the Xbox 360 (and other consoles) will be coming in both formats.

So the next big question is determining the right set for you. This all depends on the subjective layout of your home theater, lighting, budget, gaming area, and personal preference. I'll attempt to cover each of the technologies, their plusses and minuses. Most of these will be heavily related to gaming, but will also cover home theater.

An explaination of some terms:

• Burn in: Static images that, if left on over time, will leave a permanent fixed image on your screen. Examples would be health-bars or the logos of TV channels that're always in the same place.
• Convergence: Manually targeting a series of points over the screen as a whole to properly align the guns that project a picture on a TV set.
• Upconvert: Takes an incoming signal and adjusts it so it can still display it in HDTV format.
• Downconvert: Takes an incoming signal and downgrades it to be viewable by the set. Usually this means it will convert an image out of HDTV and force it into EDTV because it cannot accept a native 720p signal. But recently it also means if it receives a 1080i signal, it can downconvert it to 720p so the TV can still take advantage of the HD source.

Time to look at some of the different types of TV set:

CRT (Cathode Ray Tube) - Traditional tube based TV sets:

Advantages: These sets are terrific for gaming. They require no manual convergence and are pretty much ready to go out of the box (with a few tweaks I will get to later). The picture quality is pretty good, too. Tube based sets are still subject to burn in, but not nearly on a scale as to which Plasma's and RPTV's are. Most sets will upconvert 720p to 1080i, with most CRT's natively supporting 1080i. Contrast ratio and brightness are fabulous, and you can easily adjust the picture depending on the light source without worrying about torching the tubes over an extended period of time. You do not have to worry about dead pixels, or running out of plasma.

Disadvantages: Cost is higher than some other sets. Weight and size also plays a key issue. Some are deeper than normal. For instance, a 34" Sony HDTV clocks in at around 200 pounds. It doesn't seem like much, but with it's bulk makes it almost impossible to try and get into different positions without help of at least two people that lift weights regularly. There is still minor screen burn issues, but nothing to really worry about unless you leave the same static image on for 45 days straight. Expect though to pay about the same price for a 34" CRT HDTV depending on the brand) as you would for a 46-51" RPTV.

LCD (Liquid Crystal Display) TV's:

Advantages: Lightweight, usually a more refined picture. Depending on versatility can usually be used with a PC or set top media center. Screen burn is non existant so static images over time will not hurt the set. You do not have to run a manual convergence. Of course these sets are much smaller in scope, and very easy to carry around if you want to move your set up a lot.

Disadvantages: Most companies require a lot of dead pixels before they will take them back under warranty. Blacks are more grey-ish and are not deep or rich true blacks. Lamp replacement is usually not convered under warranty and will sometimes hit in the $300 dollar price range within 2-4 years. Depending on the set, you can really get screwed if you do not watch for low reaction times. Preferably a 16 Ms reaction time would be good enough for most gamers, but if you are an enthusiast, you may want even lower. Price is still pretty high and when comparing what can happen to an LCD set with the cost, and what is and not covered, you really have to weigh your options. Also watch for contrast ratios and CD/M brightness quality. A lot of sets on the market now and using lower tier OEM LCD screens to hit certain price points. For the most part, cheaper isn't better.

RPTV's (Rear Projection Televisions):

Advantages: Deep rich blacks that almost come close to the level of a CRT based tube TV. Very good color quality. Do not have to worry about dead pixels or plasma charge. High amount of screen display for a relatively lower cost. For instance, a Sony 34" HDTV was the same price as the Sony 51" WS520 rear projection set. Decent vertical viewability. Most parts are readily available, and if you can get a hold of a service manual, you could probably teach yourself how to repair the set. Most of these sets are very cost effective.

Disadvantages: Screen burn is more rampant than traditional tube based sets. Convergence is a must, and you will learn whether you want to or not how to converge these sets on your own. Service level convergence (where you enter the service menu of a set via a set of codes on your remote) is about 60 times better than any auto convergence or manual convergence through a regular menu system. If you move your set, be prepared to reconverge. Also, these things are massive. So if you have limited depth space, you may want to think twice. Analog television doesn't look good either. Very grainy. Games look decent as long as the set is converged. One of the major downfalls is that these sets traditionally accept 1080i native resolution only. And about 95% of them downconvert to 480p. So if you have a game which displays 720p, you are out of luck. Ask your HDTV provider if the set top they will lease you will upconvert 720 to 1080i at the source. Usually these set tops are good at doing this, albeit some loss of quality. These sets have amazing potential, but usually an ISF calibrator is needed to really see the true potential of the RPTV. These guys come to your house and spend upwards of 8-10 hours with various equipment to bring you the best picture possible. They also charge about $500.00. If you get a Best Buy rep selling you a warranty saying it includes a free ISF calibration per year, kick him or her in the genital region, head butt them in the face, and walk out of the store.

DLP (Dynamic Light Projection):

Advantages: These sets are above RPTV's in quality without the hassle of convergence. There is no possibility for screen burn. They are relatively light and thin, and put out an amazing picture. Colors are fantastic, although sometimes blacks have a bit of a problem (supposedly). They are not as bulky as a traditional CRT based set or RPTV, and resemble more of an LCD case look. There can be a bit of a rainbow effect depending on the set you purchase.

Disadvantages: Blacks sometimes have what is called a "Rainbow" effect. Meaning sometimes you can see various colors in a black because of the way DLP works depending on the reflections. Lamp replacement usually every 2-3 years at a cost of around $300.00 or so. As of this point they are pretty expensive over RPTV based sets. One of the biggest limiting factors at the moment is the way games are handled. Now, some sets are immune to this, and others are having some problems. There is sufficient lag being reported from reaction time with the controller, to the set reacting to the image and displaying said image. Some samsung's are being hit hard with this, and they have yet to react to the problem. Some sets even in the same model line up are completely immune and not showing any signs. Most, if not all, of these sets natively support 720p and upconvert to 1080i. Which can be a blessing or not depending on how it goes in the way of HDTV.

Plasma:

Advantages: Great picture display, very nice colors. Better black levels than LCD but still fail a bit in comparison next to a direct view CRT set. These are also very thin and easy to hang on a wall or attach to a mounting rack. Prices have dropped and continue to drop for Plasmas with introduction of other technologies.

Disadvantages: Screen burn susceptibility more so then RPTV's especially in initial setup. Black levels are better than LCD but still pale a bit in comparison to a direct view CRT.

Note: The EDTV trap of Plasmas has all but vanished for the most part. Make sure if you purchase a Plasma you are checking the life of the display overall, and double check to make sure the resolutions aren't off the wall numbers.

Differences between Conposite, S-video, Component, and other sources:

1.    Composite/RCA: This is the worst possible connection you can use. If your set supports S-video, please use it. Composite basically ties every signal into one cable and throws it at the set.

2.    S-video: A huge upgrade from Composite. Basically the color seperation is done within the same cable, but has it's own dedicated line. Hence it looks like a PS/2 mouse adapter plug. Every small wire that connects to the S-video female port (hot) carries it's own signal for richer color seperation and less signal degradation.

3.    Component: If you have a set that has component but does not support progressive scan, the improvement is minimal. You may as well stay with S-video. If you have a set that supports progressive scan however, switch to Component and start using 480p. The difference is amazing. Remember, you cannot display a 480p picture using S-video or composite. Only Component and up.

4.    DVI: A pure digital connection that was designed for copyright protected HD data over cable, sat, etc. It isn't going to be used much anymore unless you are a PC user.

5.    HDMI - A new digital connection that can carry the audio and the video in the same connection. Purely digital - and will most likely take hold in the coming years. You will want your set to have HDMI, if anything because it will free up component inputs.

Monster Cables:

From what I've heard, these are a complete 100% rip off. A decent shielded cable from radio shack for $19.99 perform just as good as a $150.00 monster cable which will radiate nitrous oxide from it's bowels and make you laugh at the infidels using RCA hook ups. Do not let anyone sell you on these things. There are going to be people that swear by this, and for that I will just say it is placebo effect at it's finest. If you spend that amount of money, you will be convinced it looks better just because you paid the extra cash. The only thing you want to concern yourself with is to make sure the cable is shielded to keep out surrounding noise from penetrating the cable when transmitting the signal. Gold plated connections do seem to work a little better with picture quality, but you can find the same gold plated connections for about $5.00 more.

When shopping for an HDTV set:

Basically watch out for sales tricks. After reading this post, when you go into a best buy or circuit city, you'll know more about these sets than the staff there could ever hope to know. Things to look out for:

1.    Make sure the set upconverts 720p to 1080i if the set you purchase natively supports 1080i. Although this is becoming less of a problem being that most set top boxes and consoles will do the upconverting for you, there still may be times when the TV set in question can do it better, or you may have an older set top that doesn't do this for you.

2.    Make sure the set has an HDMI input.

3.    Make sure you have enough component inputs on the set, or purchase a receiver that you can use as a switch.

4.    Warranty plans do not cover ISF calibration.

5.    Do not fall for the EDTV trap. Even though this is declining, some sets appear to be very good deals only to find when you get them home they only accept a 480p signal and are not truly high definition.

Consoles:

The Xbox 360 has been confirmed to be able to upscale games at the source. Therefore, you will not need to have a set which will scale for you. Only ime will tell how many games will come out in 720p native, or 1080i native.

Warranties:

This is kind of a tough one. 7% of people who purchase a warranty actually use them. If you can call the manufacturer to do warranty service, do it. Not a knock on technicians from super stores, but technicians from the mom and pop stores that are authorized by the manufacturer have better service, follow through, and want to see you happy. On a side note, if you can purchase a set from one of these smaller stores, you may pay an additional $100-200 more, but the service you receive for the life of your product will pay for it in the long run.

Just because a set has component input, doesn't mean that the set supports 480p. If you are looking for a lower end set, some can be deceiving. Make sure you verify if a set can support 480 progressive.

Also a quick word on DVD players. There is a new product out there with regard to DVD players that will upconvert a DVD to 1080i or 720p at the source. This will usually require an HDMI connection.

A lot of people are buying into these thinking they will be able to pop in their DVD's and instantly get HD resolution. This couldn't be further from the truth. In actuality, a 480i source (DVD) being upconverted to 720p or 1080i at the DVD player itself and then passed through another cable looks no different in blind tests than a good 480p DVD player. The thing with this is, most of these players are terrible when used through their component outputs. Depending on where you go, HDMI cables can cost a fortune. Even online. Be careful.

A word on Avia and calibration DVD programs:

There are DVD's that you can purchase that come with tinted colored glasses that guide you through a process to get the best picture out of your set for whichever room you have it in. It will go through brightness levels, contrast, tint, color, sharpness, etc - and at the end you will have an optimized picture.

THX DVD's comes with their own optimizer if you do not want to spend extra money on personal calibration. You can run these tests from any normal DVD player and select the THX options from the DVD movie itself.

THX also has a sound test to make sure you have correctly set up your sound system. While not as in depth as something on Avia, you still have enough to work with to make sure your speakers are correctly place.

 

50 Common Interview Questions and Answers

50 Common Interview Questions and Answers :

Review these typical interview questions and think about how you would answer them. Read the questions listed; you will also find some strategy suggestions with it.

1. Tell me about yourself:

The most often asked question in interviews. You need to have a short statement prepared in your mind. Be careful that it does not sound rehearsed. Limit it to work-related items unless instructed otherwise. Talk about things you have done and jobs you have held that relate to the position you are interviewing for. Start with the item farthest back and work up to the present.

2. Why did you leave your last job?

Stay positive regardless of the circumstances. Never refer to a major problem with management and never speak ill of supervisors, co- workers or the organization. If you do, you will be the one looking bad. Keep smiling and talk about leaving for a positive reason such as an opportunity, a chance to do something special or other forward- looking reasons.

3. What experience do you have in this field?

Speak about specifics that relate to the position you are applying for. If you do not have specific experience, get as close as you can.

4. Do you consider yourself successful?

You should always answer yes and briefly explain why. A good explanation is that you have set goals, and you have met some and are on track to achieve the others.

5. What do co-workers say about you?

Be prepared with a quote or two from co-workers. Either a specific statement or a paraphrase will work. Jill Clark, a co-worker at Smith Company, always said I was the hardest workers she had ever known. It is as powerful as Jill having said it at the interview herself.

6. What do you know about this organization?

This question is one reason to do some research on the organization before the interview. Find out where they have been and where they are going. What are the current issues and who are the major players?

7. What have you done to improve your knowledge in the last year?

Try to include improvement activities that relate to the job. A wide variety of activities can be mentioned as positive self-improvement. Have some good ones handy to mention.

8. Are you applying for other jobs?

Be honest but do not spend a lot of time in this area. Keep the focus on this job and what you can do for this organization. Anything else is a distraction.

9. Why do you want to work for this organization?

This may take some thought and certainly, should be based on the research you have done on the organization. Sincerity is extremely important here and will easily be sensed. Relate it to your long-term career goals.

10. Do you know anyone who works for us?

Be aware of the policy on relatives working for the organization. This can affect your answer even though they asked about friends not relatives. Be careful to mention a friend only if they are well thought of.

11. What kind of salary do you need?
A loaded question. A nasty little game that you will probably lose if you answer first. So, do not answer it. Instead, say something like, That's a tough question. Can you tell me the range for this position? In most cases, the interviewer, taken off guard, will tell you. If not, say that it can depend on the details of the job. Then give a wide range.

12. Are you a team player?
You are, of course, a team player. Be sure to have examples ready. Specifics that show you often perform for the good of the team rather than for yourself are good evidence of your team attitude. Do not brag, just say it in a matter-of-fact tone. This is a key point.

13. How long would you expect to work for us if hired?

Specifics here are not good. Something like this should work: I'd like it to be a long time. Or As long as we both feel I'm doing a good job.

14. Have you ever had to fire anyone? How did you feel about that?

This is serious. Do not make light of it or in any way seem like you like to fire people. At the same time, you will do it when it is the right thing to do. When it comes to the organization versus the individual who has created a harmful situation, you will protect the organization. Remember firing is not the same as layoff or reduction in force.

15. What is your philosophy towards work?

The interviewer is not looking for a long or flowery dissertation here. Do you have strong feelings that the job gets done? Yes. That's the type of answer that works best here. Short and positive, showing a benefit to the organization.

16. If you had enough money to retire right now, would you?

Answer yes if you would. But since you need to work, this is the type of work you prefer. Do not say yes if you do not mean it.

17. Have you ever been asked to leave a position?

If you have not, say no. If you have, be honest, brief and avoid saying negative things about the people or organization involved.

18. Explain how you would be an asset to this organization.

You should be anxious for this question. It gives you a chance to highlight your best points as they relate to the position being discussed. Give a little advance thought to this relationship.

19. Why should we hire you?

Point out how your assets meet what the organization needs. Do not mention any other candidates to make a comparison.

20. Tell me about a suggestion you have made.

Have a good one ready. Be sure and use a suggestion that was accepted and was then considered successful. One related to the type of work applied for is a real plus.

21. What irritates you about co-workers?

This is a trap question. Think real hard but fail to come up with anything that irritates you. A short statement that you seem to get along with folks is great.

22. What is your greatest strength?

Numerous answers are good, just stay positive. A few good examples: Your ability to prioritize, Your problem-solving skills, Your ability to work under pressure, Your ability to focus on projects, Your professional expertise, Your leadership skills, Your positive attitude

23. Tell me about your dream job.

Stay away from a specific job. You cannot win. If you say the job you are contending for is it, you strain credibility. If you say another job is it, you plant the suspicion that you will be dissatisfied with this position if hired. The best is to stay genetic and say something like: A job where I love the work, like the people, can contribute and can't wait to get to work.

24. Why do you think you would do well at this job?

Give several reasons and include skills, experience and interest.

25. What are you looking for in a job?

See answer # 23

26. What kind of person would you refuse to work with?

Do not be trivial. It would take disloyalty to the organization, violence or lawbreaking to get you to object. Minor objections will label you as a whiner.

27. What is more important to you: the money or the work?

Money is always important, but the work is the most important. There is no better answer.

28. What would your previous supervisor say your strongest point is?

There are numerous good possibilities:
Loyalty, Energy, Positive attitude, Leadership, Team player, Expertise, Initiative, Patience, Hard work, Creativity, Problem solver

29. Tell me about a problem you had with a supervisor.

Biggest trap of all. This is a test to see if you will speak ill of your boss. If you fall for it and tell about a problem with a former boss, you may well below the interview right there. Stay positive and develop a poor memory about any trouble with a supervisor.

30. What has disappointed you about a job?

Don't get trivial or negative. Safe areas are few but can include:
Not enough of a challenge. You were laid off in a reduction Company did not win a contract, which would have given you more responsibility.

31. Tell me about your ability to work under pressure.

You may say that you thrive under certain types of pressure. Give an example that relates to the type of position applied for.

32. Do your skills match this job or another job more closely?

Probably this one. Do not give fuel to the suspicion that you may want another job more than this one.

33. What motivates you to do your best on the job?

This is a personal trait that only you can say, but good examples are: Challenge, Achievement, Recognition

34. Are you willing to work overtime? Nights? Weekends?

This is up to you. Be totally honest.

35. How would you know you were successful on this job?

Several ways are good measures:
You set high standards for yourself and meet them. Your outcomes are a success.Your boss tell you that you are successful

36. Would you be willing to relocate if required?

You should be clear on this with your family prior to the interview if you think there is a chance it may come up. Do not say yes just to get the job if the real answer is no. This can create a lot of problems later on in your career. Be honest at this point and save yourself uture grief.

37. Are you willing to put the interests of the organization ahead of your own?

This is a straight loyalty and dedication question. Do not worry about the deep ethical and philosophical implications. Just say yes.

38. Describe your management style.

Try to avoid labels. Some of the more common labels, like progressive, salesman or consensus, can have several meanings or descriptions depending on which management expert you listen to. The situational style is safe, because it says you will manage according to the situation, instead of one size fits all.

39. What have you learned from mistakes on the job?

Here you have to come up with something or you strain credibility. Make it small, well intentioned mistake with a positive lesson learned. An example would be working too far ahead of colleagues on a project and thus throwing coordination off.

40. Do you have any blind spots?

Trick question. If you know about blind spots, they are no longer blind spots. Do not reveal any personal areas of concern here. Let them do their own discovery on your bad points. Do not hand it to them.

41. If you were hiring a person for this job, what would you look for?

Be careful to mention traits that are needed and that you have.

42. Do you think you are overqualified for this position?

Regardless of your qualifications, state that you are very well qualified for the position.

43. How do you propose to compensate for your lack of experience?

First, if you have experience that the interviewer does not know about, bring that up: Then, point out (if true) that you are a hard working quick learner.

44. What qualities do you look for in a boss?

Be generic and positive. Safe qualities are knowledgeable, a sense of humor, fair, loyal to subordinates and holder of high standards. All bosses think they have these traits.

45. Tell me about a time when you helped resolve a dispute between others.

Pick a specific incident. Concentrate on your problem solving technique and not the dispute you settled.

46. What position do you prefer on a team working on a project?

Be honest. If you are comfortable in different roles, point that out.

47. Describe your work ethic.

Emphasize benefits to the organization. Things like, determination to get the job done and work hard but enjoy your work are good.

48. What has been your biggest professional disappointment?

Be sure that you refer to something that was beyond your control. Show acceptance and no negative feelings.

49. Tell me about the most fun you have had on the job.

Talk about having fun by accomplishing something for the organization.

50. Do you have any questions for me?

Always have some questions prepared. Questions prepared where you will be an asset to the organization are good. How soon will I be able to be productive? and What type of projects will I be able to assist on? are examples.

And Finally Good Luck

 

Digital Camera Buyers Guide

Digital Camera Buyers Guide

So, it's time for a digital camera huh? Well, buying one can be more than a little difficult. What types of features should you look for? Well, this guide will tell you that plus get you a little more familiar with what these cameras are capable of.

Megapixels :

When it comes to megapixels, the more the better. I recommend a minimum of 2, but 3 or 4 is great. We did a test to see if a camera with 2.3 megapixels (actually 1.92 - 1600 x 1200) could produce a good quality 8x10.

Turns out it can, if you have the right paper and printer. We used HP Premium Plus photo paper with an HP 970 series printer and made a fantastic 8 x 10. Remember, I was a professional photographer before I got into computing, so I know a good print when I see it :-)

The resolution at 8x10 (we had to crop in to make the picture proportional to 8x10) was only 150 DPI. Most printers would not make a real good 8x10 at that resolution, but this one did. So, if you want to be sure you can get good 8 x 10s, you may want to go with a 3 megapixel camera or better (that gives you around 200 DPI at 8x10 size, still not quite the optimum 300 DPI, but it looks good with the right printer).

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Optical vs Digital Zoom

You've probably noticed that most digital cameras have both a specification for digital and optical zoom. Pay the most attention to the optical zoom.

The optical zoom magnifies (zooms in) using glass. The digital zoom basically crops out the edge of the picture to make the subject appear closer, causing you to lose resolution or to get an interpolated resolution (i.e. the camera adds pixels). Neither of which help image quality.

Finally, make sure you get enough (optical) zoom. A 2x zoom isn't going to do much for you. A 3x is the average you'll find in most digital cameras will probably be good for most uses. More on lenses later.

Connection :

How does the camera connect to your computer? If you have a USB port in your computer, you'll want a camera that can connect via USB as opposed to a slow serial connection.

On the other hand, if your computer doesn't have a USB port, is there a serial connector available for the camera you're looking at? If so, is it a special order and how long does it take to get it?

Storage :

What does the camera use to store images with? If it uses a memory stick, make sure you consider buying additional sticks when you get your camera. A typical 8 meg memory stick that comes with a 2 megapixel camera only holds 5 or 6 images at the camera's best quality.

Some cameras use a 3.5 inch disk for storage. Be careful of these! Although it may sound like a good idea, a 3 megapixel camera at high resolution produces a 1 meg file (compressed!). That's only 1 picture per disk.

Here's a few more things to look out for when trying to make your digital camera purchase.

Picture Formats :

When you're trying to decide on which digital camera to get, check and see how many different picture formats it supports.

You want something that can produce both uncompressed (usually TIFF) and compressed (usually JPEG) images. I personally use the high quality JPEG setting on my camera for most of my shooting. TIFFs are just too big and the difference in quality is not ascertainable by mere mortals.

You also want to be able to shoot at a lower resolution than the camera's maximum. That way, If you're running short on memory, you can squeeze a few more shots on your memory stick.

Auxiliary Lens / Flash :

This was a biggie for me. While a 3x zoom may work for the "average" user, I needed something that allowed me to do some wide angle work as well as have a good telephoto lens.

So, the camera I purchased a few months back was a Nikon Coolpix 990 (note that this isn't the only camera that can accept lenses). It has auxiliary lenses that screw into the filter ring on the front of the lens. I now have an ultra-wide fisheye lens plus a nice telephoto.

In addition to lenses, I wanted a good flash. The flash that is built into most of these cameras gives you a top range of 15-20 feet - at best. I wanted a camera that could take a powerful auxiliary flash (again, the Nikon isn't the only camera that fits this requirement, but I liked it better than the rest). If you need more reach than the small built in flash can deliver, then make sure you can attach an external flash to any camera you consider.

As an added bonus, if you get a camera that can take an external flash, you can place that flash on a bracket and eliminate red-eye.

Flash Distance :

Speaking of flashes, make sure you check the distance the built in flash is good for. You don't want a camera with a wimpy flash that only travels a few feet (well, unless you can get an external flash for it as described above).

Battery Type

This may not sound important, but it is. Anyone who owns a digital camera can tell you they eat batteries the way a sumo wrestler eats at a buffet.

Make sure the camera can run on regular (or rechargeable) "AA" type batteries. You don't want a camera that eats through expensive lithium batteries every 10 shots or so.

One thing to remember about digital cameras, they do eat through batteries. I recommend getting some Nickel Metal Hydride rechargeable for it. I have some for mine and they have saved me a fortune.

Final Notes:

Choosing a digital camera isn't easy. There's a huge selection out there and only you can determine which features you need.

For instance, if you shoot wildlife photos, a small 3x zoom probably isn't going to cut it (unless you can attach auxiliary lenses to it). If you shoot lots of close-ups, make sure the camera has some sort of macro capability. If you shoot big group photos indoors, an external flash may be necessary.

My advice is to make a list of things you want to be able to do with the camera then go to somewhere that can help you make a good purchase decision.

Finally, buy the BEST camera you can possibly afford. Or wait until the price drops on one with the type of features you want.